Technical Considerations Associated with Risk Management of Induced Seismicity in Waste-Water Disposal & Hydraulic Fracturing Operations

Transcription

1 Technical Considerations Associated with Risk Management of Induced Seismicity in Waste-Water Disposal & Hydraulic Fracturing Operations K. J. (Kris) Nygaard, Sr. Stimulation Consultant ExxonMobil Production Company Groundwater Protection Council Annual Forum St. Louis, Missouri September 23-25, 2013 This presentation includes forward-looking statements. Actual future conditions (including economic conditions, energy demand, and energy supply) could differ materially due to changes in technology, the development of new supply sources, political events, demographic changes, and other factors discussed herein (and in Item 1 of ExxonMobil s latest report on Form 10-K). This material is not to be reproduced without the permission of Exxon Mobil Corporation. Exxon Mobil Corporation has numerous subsidiaries, many with names that include ExxonMobil, Exxon, Esso and Mobil. For convenience and simplicity in this presentation, the parent company and its subsidiaries may be referenced separately or collectively as "ExxonMobil." Abbreviated references describing global or regional operational organizations and global or regional business lines are also sometimes used for convenience and simplicity. Nothing in this presentation is intended to override the corporate separateness of these separate legal entities. Working relationships discussed in this presentation do not necessarily represent a reporting connection, but may reflect a functional guidance, stewardship, or service relationship.

2 Background Seismicity can be induced or triggered when stress or pore changes promote slip along a fault. These changes can be due to: Geothermal energy Carbon Capture Storage Mining Dam/reservoir impoundment Waste water disposal wells O&G injection/extraction Hydraulic fracturing National Academy of Sciences Report Major Findings NAS has recently examined induced across multiple energy sectors. Three major findings were published from this study (1) : 1. The process of hydraulic fracturing a well as presently implemented for shale gas recover does not pose a high risk for inducing felt seismic events 2. Injection of disposal of waste water derived from energy technologies into the subsurface does pose some risk for induced, but very few events have been documented over the past several decades relative to the large number of disposal wells in operation; and 3. CCS, due to the large net volumes of injected fluids, may have potential for inducing larger seismic events. (1) NAS (June 2012), Induced Seismicity Potential in Energy Technologies, 2

3 Historical Examples Documented examples of seismic activity that have been linked to human activities include: 70 hydrocarbon fields with unusually large seismic activity; primarily in 2 basins (2) 95 artificial water reservoirs with reported reservoir triggered (3) 26 sites in the US with mining related events larger than Magnitude 2.6 (4) 25 geothermal energy sites with injection related events larger than Magnitude 0 (1) Understanding whether individual events are triggered, induced, or naturally occurring can be challenging Although the study of induced has been ongoing since the 1960s, many questions still remain References: 2. Jenny Suckale, Chapter 2 - Induced Seismicity in Hydrocarbon Fields, In: Renata Dmowska, Editor(s), Advances in Geophysics, Elsevier, 2009, Volume 51, Pages , ISSN , ISBN , /S (09) Gupta, H. K., A review of recent studies of triggered earthquakes by artificial water reservoirs with special emphasis on earthquakes in Koyna, India, Earth-Science Reviews 58 (2002) Routine United States Mining Seismicity, State-By-State List of Mining Regions, USGS Earthquake Hazard Program, 3

4 Injection Operations Waste Water Disposal & Hydraulic Fracturing Disposal Operations Injection into non-productive intervals to dispose of produced water and cuttings Pressure of injection typically below frac Injection operations continue for months to years Volumes ~ 100,000 1,000,000 barrels/year Injected fluids can reach ~1000s ft from injection ~140,000 Class II injection wells operating in US Aquifer Confining zone Disposal zone Producing zone Hydraulic Fracturing Operations Stimulation treatment for low permeability reservoirs (i.e., shale gas, tight oil) Treatment s above fracturing to create fractures in the reservoir Stimulation operations typically last hours; for multiple stages it can take several days to complete a single well Volumes ~ 1000s of barrels per stage Fracture length created ~100s ft from wellbore 4

5 Event Impact Ground Motion and Potential Damage Primary Structure Design fundamentally based on probabilistic seismic analysis defined by a hazard curve: Defines the probability of exceeding spectral acceleration at a specified structural period Analysis based on seismic sources with associated activities probabilistically defined Lower limit for earthquakes < Mag. 4 Induced, typically below Mag. 4, likely to have little to no impact on primary structure Potential Damage None MMI Perceived Shaking Description of Intensity Level I Not Felt Not felt except by a very few under especially favorable conditions. II III IV Weak Light Very Light V Moderate Light VI Strong Felt only by a few persons at rest, especially on upper floors of buildings. Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably. Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop. Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight. Humans & Secondary Components Likely to be more sensitive to small tremors Highly dependent on Local soil conditions In-structure local motion amplification Best monitored via ground motions Effects described by Modified Mercalli Intensity (MMI) Moderate Moderate/ Heavy VII VIII Very Strong Severe Heavy IX Violent Very Heavy X XI XII Extreme Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned. Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent. Few, if any (masonry) structures remain standing. Bridges destroyed. Rails bent greatly. Damage total. Lines of sight and level are distorted. Objects thrown into the air. Wald, D.J., Worden, B.C., Quitoriano, V., and Pankow, K.L., 2005, ShakeMap manual: technical manual, user's guide, and software guide: U.S. Geological Survey, 132 p. Wald, D.J., Quitoriano, V., Heaton, T.H., and Kanamori, H., 1999, Relationship between Peak Ground Acceleration, 5 Peak Ground Velocity, and Modified Mercalli Intensity in California: Earthquake Spectra, v. 15, no. 3, p

6 Event Impact Ground Motion and Potential Damage Primary Structure Design fundamentally based on probabilistic seismic analysis defined by a hazard curve: Defines the probability of exceeding spectral acceleration at a specified structural period Analysis based on seismic sources with associated activities probabilistically defined Lower limit for earthquakes < Mag. 4 Induced, typically below Mag. 4, likely to have little to no impact on primary structure Humans & Secondary Components Likely to be more sensitive to small tremors Highly dependent on Local soil conditions In-structure local motion amplification Best monitored via ground motions Effects described by Modified Mercalli Intensity (MMI) Potential Damage None MMI Perceived Shaking Approximate Magnitude* Peak Acceleration (%g) Peak Velocity (cm/s) I Not Felt <0.17 <0.1 II III IV Light Very Light V Moderate Light VI Strong Moderate VII Very Strong Moderate/ Heavy VIII Severe Heavy IX Violent X Very Heavy XI Extreme >7.0 >124 >116 XII Weak *Magnitudes correspond to intensities that are typically observed at locations near the epicenter of earthquakes of these magnitudes Wald, D.J., Worden, B.C., Quitoriano, V., and Pankow, K.L., 2005, ShakeMap manual: technical manual, user's guide, and software guide: U.S. Geological Survey, 132 p. Wald, D.J., Quitoriano, V., Heaton, T.H., and Kanamori, H., 1999, Relationship between Peak Ground Acceleration, 6 Peak Ground Velocity, and Modified Mercalli Intensity in California: Earthquake Spectra, v. 15, no. 3, p

7 Risk Management Probability and Consequences Risk is the combination of Probabilities and Consequences A standard tool used in risk assessment is a risk matrix approach to identify risk level With risk level identified, possible risk mitigation approaches can be evaluated Consequence 1 MMI > VIII PGA > ~0.34g 2 MMI : VI - VII PGA > ~0.092g 3 MMI: V-VI PGA > ~0.039g 4 MMI: II-V PGA < ~0.039g Very Likely Probability Somewhat Likely Somewhat A Generic Example of a Possible Risk Matrix Very High High High Medium Low High High Medium Low Very Low Medium Medium Low Very Low Very Low Low Very Low Very Low Very Low Very Low 7

8 Potential Probability Considerations Probability A Very Likely B Somewhat Likely C Fluid Volume Large volumes of injection in immediate or close proximity to active faults. Reservoir rising and approaching fracture Large or moderate volumes of fluid injected in proximity to active faults. Reservoir rising above initial Moderate fluid volume of injection; remote from any active fault. Reservoir is near initial reservoir Formation Character Deeper injection horizon; highly consolidated formations. Low KH sand of limited lateral Moderate depth injection horizons; highly consolidated formations. Marginal KH sand of marginal lateral Shallow injection horizon; highly consolidated formations. Moderate KH sand with moderate lateral Tectonic / Faulting / Soil Conditions Large-scale developed/active faults are present at depths that could be influenced by / fluid communication associated with injection; strongly consolidated formation; soil conditions amplify vibrational modes Large-scale developed/active faults may possibly be present, but not identified; strongly consolidated formation, soil conditions may amplify vibrational modes Faults well identified, and unlikely to be in influenced by / fluid associated with injection; moderately consolidated formation Operating Experience Past injection experience in region with damaging levels of ground shaking Limited injection in region Significant injection in region with no damaging levels of ground shaking Public Sensitivity & Tolerance High population density & historically low background Moderate / high population density and/or historically low / moderate background Moderate population density and historically moderate / high background Local Construction Standards Primitive construction and limited/no engineering applied for earthquake resistant designs Sound construction practices, but age/vintage of building construction pre-dates earthquake engineering design principles. Ground vibration and seismic activity routinely considered in civil / structural designs and in majority of buildings D Very Small fluid volume of injection; remote from any active fault. Reservoir is constant below initial Shallow injection horizon; weakly consolidated formations. Good KH sand with good lateral Stable stress environment; minimal faulting; if faults present, too small to induce any surface felt ; weakly consolidated or unconsolidated formation, soil conditions may dampen vibrational modes Significant injection in region with no surface felt ground shaking Low population density & historically moderate background Rigorous earthquake engineering civil / structural designs and required E Very Highly Small fluid volume of injection; remote from any active faults. Reservoir is constant below initial Shallow injection horizon, Poorly consolidated formations. High KH sand of extensive lateral Stable stress environment; no significant faults, weakly consolidated or unconsolidated formation, soil conditions may dampen vibrational modes 8 Significant injection across wide geographic region with no surface felt ground shaking Low population density & historically high background Rigorous earthquake engineering civil / structural designs and required

9 Potential Probability Considerations Probability A Very Likely B Somewhat Likely C Fluid Volume Large volumes of injection in immediate or close proximity to active faults. Reservoir rising and approaching fracture Large or moderate volumes of fluid injected in proximity to active faults. Reservoir rising above initial Moderate fluid volume of injection; remote from any active fault. Reservoir is near initial reservoir Formation Character Deeper injection horizon; highly consolidated formations. Low KH sand of limited lateral Moderate depth injection horizons; highly consolidated formations. Marginal KH sand of marginal lateral Shallow injection horizon; highly consolidated formations. Moderate KH sand with moderate lateral Tectonic / Faulting / Soil Conditions Large-scale developed/active faults are present at depths that could be influenced by / fluid communication associated with injection; strongly consolidated formation; soil conditions amplify vibrational modes Large-scale developed/active faults may possibly be present, but not identified; strongly consolidated formation, soil conditions may amplify vibrational modes Faults well identified, and unlikely to be in influenced by / fluid associated with injection; moderately consolidated formation Operating Experience Operating Experience Past injection experience in region with damaging levels of ground shaking Limited injection in region Significant injection in region with no damaging levels of ground shaking Public Sensitivity & Tolerance Past injection experience in region with damaging levels of ground shaking High population density & historically low background Limited injection in region Moderate / high population density and/or historically low / moderate background Significant injection in region with no damaging levels of ground shaking Moderate population density and historically moderate / high background Local Construction Standards Primitive construction and limited/no engineering applied for earthquake resistant designs Sound construction practices, but age/vintage of building construction pre-dates earthquake engineering design principles. Ground vibration and seismic activity routinely considered in civil / structural designs and in majority of buildings D Very Small fluid volume of injection; remote from any active fault. Reservoir is constant below initial Significant injection in region with no surface felt ground shaking Shallow injection horizon; weakly consolidated formations. Good KH sand with good lateral Stable stress environment; minimal faulting; if faults present, too small to induce any surface felt ; weakly consolidated or unconsolidated formation, soil conditions may dampen vibrational modes Significant injection in region with no surface felt ground shaking Low population density & historically moderate background Rigorous earthquake engineering civil / structural designs and required E Very Highly Small fluid volume of injection; remote from any active faults. Reservoir is constant below initial Shallow injection horizon, Stable stress environment; no Poorly Significant consolidated injection significant faults, experience weakly historically across formations. High KH consolidated or unconsolidated sand wide of extensive geographic lateral formation, region soil conditions with may no surface felt ground dampen vibrational modes shaking 9 Significant injection across wide geographic region with no surface felt ground shaking Low population density & historically high background Rigorous earthquake engineering civil / structural designs and required

10 Potential Probability Considerations Probability A Very Likely B Somewhat Likely C D Very E Very Highly Fluid Volume Large volumes of injection in immediate or close proximity to active faults. Reservoir rising and approaching fracture Large or moderate volumes of fluid injected in proximity to active faults. Reservoir rising above initial Moderate fluid volume of injection; remote from any active fault. Reservoir is near initial reservoir Small fluid volume of injection; remote from any active fault. Reservoir is constant below initial Small fluid volume of injection; remote from any active faults. Reservoir is constant below initial modes Formation Character Shallow injection horizon; highly consolidated formations. Moderate KH sand with moderate lateral Shallow injection horizon, Poorly consolidated formations. High KH sand of extensive lateral Tectonic / Faulting / Soil Conditions Faults well identified, and unlikely to be in influenced by / fluid associated with injection; moderately consolidated formation Stable stress environment; no significant faults, weakly consolidated or unconsolidated formation, soil conditions may dampen vibrational modes 10 Operating Experience Tectonic / Faulting / Soil Conditions Significant injection in region with no damaging levels of ground shaking Significant injection across wide geographic region with no surface felt ground shaking Public Sensitivity & Tolerance Moderate / high population density and/or historically low / moderate background Moderate population density and historically moderate / high background Low population density & historically high background Local Construction Standards Deeper injection horizon; Large-scale developed/active faults Past injection High population Large-scale highly consolidated developed/active are present at depths faults that could are be present experience in region at depths density & historically that could formations. Low KH sand influenced by / fluid with damaging levels low background be influenced of limited lateral by communication / fluid associated communication with of ground shaking associated with injection; strongly consolidated injection; strongly consolidated formation; soil conditions formation; amplify soil conditions amplify vibrational modes vibrational modes Moderate depth injection Large-scale developed/active faults Limited injection Large-scale horizons; developed/active highly may possibly be faults present, but not may experience possibly historically be present, but not consolidated formations. identified; strongly consolidated in region identified; Marginal strongly KH sand of consolidated formation, soil conditions formation, may soil conditions may marginal lateral amplify vibrational modes amplify vibrational modes Faults well identified, and unlikely to be in influenced by / fluid associated with injection; moderately consolidated formation Primitive construction and limited/no engineering applied for earthquake resistant designs Sound construction practices, but age/vintage of building construction pre-dates earthquake engineering design principles. Ground vibration and seismic activity routinely considered in civil / structural designs and in majority of buildings Shallow injection horizon; Stable stress environment; minimal Significant injection Low population Stable stress weakly consolidated environment; faulting; if faults minimal present, too small faulting; experience if historically faults density present, & historically too formations. Good KH to induce any surface felt in region with no moderate small to induce sand with good any lateral surface ; weakly felt consolidated ; or surface weakly felt ground consolidated background or unconsolidated formation, soil shaking unconsolidated formation, conditions soil may dampen conditions vibrational may dampen vibrational modes modes Stable stress environment; no significant faults, weakly consolidated or unconsolidated formation, soil conditions may dampen vibrational Rigorous earthquake engineering civil / structural designs and required Rigorous earthquake engineering civil / structural designs and required

11 Potential Consequence Considerations Consequence Safety / Health Environmental Public Financial 1 Mod. Merc. Ind. > VIII Potential fatalities and serious injuries; building structural damage. Potential widespread long-term significant adverse affects. Possible release of potentially hazardous compounds extended duration &/or large volumes in affected area (large chemical static / transport vessels and pipelines break). Ground shaking felt in large region. Possible extensive mobilization of emergency 1 st responders. Possible disruption of community services for extended time. $$$$ 2 Mod. Merc. Ind. VI VII 3 Mod. Merc. Ind. V VI 4 Mod. Merc. Ind. < V Potential serious injuries; building cosmetic & secondary building content damage. Potential minor injuries in isolated circumstances; building secondary content damage. Potential first aid in isolated circumstances; isolated secondary building content damage. Potential localized medium term significant adverse effects. Possible release of potentially hazardous compounds shortduration &/or limited volumes (large vessels break). Possible release of potentially hazardous compounds in limited volumes (e.g., containers break). Possible release of potentially hazardous compounds in very small volumes (e.g., small containers break). 11 Ground shaking felt by all in local area. Possible mobilization of emergency 1 st responders. Possible disruption of community services for brief time. Ground shaking possibly felt by sensitive few at site. Possible limited site impact and possible limited mobilization of 1 st responder(s). Possible minor public complaints. $$$ $$ $

12 Potential Stoplight Systems and Mitigation Approaches With risk level identified, possible risk mitigation approaches can be evaluated (effectiveness / cost) A stoplight approach is prudent and reasonable in high risk areas Options for monitoring systems can include human observation, use of existing regional array, local surface arrays, or downhole arrays; and can be selected based on considering specific local conditions HIGH MEDIUM LOW VERY LOW Consider suspending operations; mitigate to reduce risk Adjust operations; consider steps to mitigate risk Operations continue as normal Operations continue as normal 12

13 Case Studies Waste Disposal and Hydraulic Fracturing Industry Data Disposal 1. Dallas-Forth Worth Airport, Texas 2. Dallas-Fort Worth, Cleburne, TX 3. Braxton, West Virginia 4. Guy-Greenbriar, Arkansas 5. General Case Injection Well 6a, b 4 1, 2 3 Hydraulic Fracturing 6. Horn River Basin, Canada a) Etsho b) Tattoo 7. Bowland Shale, UK 8. General Case HF Well - Microseisms always created 7 13

14 Example Assessments Waste-Water Disposal & Hydraulic Fracturing Note: assessment of probability & consequence for the specific examples based on hindcast evaluation of observed and publicly-reported information. 14

15 Recent Examples of Hydraulic Fracturing Related Stoplight Systems and Monitoring Approaches Suspend Operations M L 4.0 Proceed with Caution 2.0 M L 4.0 Proceed as Planned M L 2.0 Suspend Operations M L 0.5 Continue with Recommended Operations and Monitoring M L 0.5 Horn River, Canada Canadian National Seismograph Network, Active Stations, 2/6/13 Bowland Shale, UK The controls are not at this stage to be regarded as definitive, but as appropriate precautionary measures for our present state of knowledge -Ministry Statement* Regional monitoring system Events should be reliably detected and reported at M L 2.0 Commission contacts operator if detected; at M L 2.0, mitigation discussions begin Unique response for each case Operations temporarily suspended for M L 4.0 Additional controls required as part of standard operating procedure Flow-back between frac stages required to relieve Background and real-time seismic monitoring required, with detection -1.0 M L 1.0 Flow-back requirement creates operational complexity * 15

16 Perspectives Approaches to assess and manage risk should be encouraged, be based on sound science, and take into account the local conditions, operational scope, geological setting, historical baseline levels; and reflect reasonable and prudent consideration of engineering standards and codes related to structural health. Seismicity monitoring and mitigation should be considered in local areas where induced is of significant risk, such as in areas where: Significant (above historical baseline levels) has actually occurred and sound technical assessment indicates that the is associated with fluid injection operations, or If sound technical assessment indicates the local area may possess significant risk associated with potential induced. In local areas where induced is of significant risk, appropriate monitoring and mitigation should include: A mechanism to alert the operator in near real-time to the occurrence of significantly above local historical baseline levels, and A procedure to modify and/or suspend operations if levels increase above threshold values for maintaining local structural health integrity and minimizing secondary damage Mitigation controls, if implemented, should consider completion practices and operational complexity 16